Methods and Systems for Preventing Iron Oxide Formulation and Decarburization During Steel Tempering

ABSTRACT

The technology described herein provides a method and system to prevent iron oxide formation and decarburization during strand heat treating of a steel product without the subsequent required use of acid pickling, which has associated health and environmental risks. Additionally, this technology provides placing a coating, such as copper plating, to the surface of a steel wire prior to strand heat treating to avoid both iron oxide formation and decarburization through the surface of the steel wire by preventing interactions between the steel wire and the furnace atmosphere. To remove oxides formed by the plating metal, the oxides are chemically reduced by passing the steel wire through a reducing gas, electrolytically reduced by plating with the wire anodic, mechanically reduced through the use of brushes, or the like, or chemically reduced by acid pickling.

FIELD OF THE INVENTION

The technology described herein relates generally to metal heat treatingprocesses such as annealing, patenting, or tempering. More specifically,the technology described herein relates to a method and system toprevent iron oxide formation and decarburization during strand heattreating of a steel product without the required use of acid pickling.Additionally, this technology relates to placing a coating, such ascopper plating, to the surface of a steel wire prior to strand heattreating to avoid both iron oxide formation and decarburization throughthe surface of the steel wire by preventing interactions between thesteel wire and the furnace atmosphere.

BACKGROUND OF THE INVENTION

Patenting is a heat treatment process for a metal or alloy. Patenting isused to soften a steel metal or alloy and remove any existingbrittleness. Control of both time and temperature during the patentingprocess is critical in order to achieve a final product with appropriatemechanical properties. Patenting is, for example, but not limited to,used for the strand annealing process used during the manufacture ofsteel tire cord to strengthen the tire cord. For example, during themanufacture of steel tire cord, copper or brass is generallyelectroplated on the surface of the wire in-line after the heat-treatingprocess in order to promote adhesion of the wire to the rubber of thetire. In general, the process steps known in the art, from the beginningof wire heat treating through the application of electrolytic copper,include: austenitizing, controlled cooling to 500° C. to 650° C., waterquenching to room temperature, acid pickling, water rinsing, andelectrolytic copper pyrophosphate plating.

The most common method of strand annealing, patenting, or tempering isto heat wire in a direct-fired gas strand-patenting furnace to about1000° C. This process is termed austenitizing. Austenitizing isimmediately followed by controlled cooling to within the range of 500°C. to 650° C., depending upon the specific steel chemistry. Whileaustenitizing with known, current technology, the surface of the steelwire is in direct contact with the atmosphere within the furnace. Theatmosphere within the furnace contains oxidizing gases, like oxygen, O₂,and carbon dioxide, CO₂, and decarburizing gases like water vapor.Decarburization is the decreasing content of carbon, C, in the steelwire. However, it is desired to prevent both the formation of ironoxides and decarburization due to exposure of the wire within theatmosphere of the furnace.

The iron oxide formed in the furnace must subsequently be removed. Thisis generally accomplished by exposing the steel wire cord to hot,concentrated hydrochloric acid, HCl, or sulfuric acid, H₂SO₄. Iron oxidemay form as FeO, Fe₂O₃, and/or Fe₃O₄. It is also common to useelectrolytic acid pickling in conjunction with sulfuric acid, H₂SO₄.Acid pickling is a process used on metallic surfaces to removeimpurities and stains, such as rust or iron oxides, before subsequentmetal processing, such as plating, drawing, extrusion, or rolling.Formation of iron oxide removes usable material from the surface of thewire, thereby reducing the mass of steel available for subsequentconversion to other products. Pickling acids, such as concentratedhydrochloric acid, HCl, or sulfuric acid, H₂SO₄, are expensive andenvironmentally unfriendly. Furthermore, such pickling acids createmaintenance and health issues related to disposal, potential spills, andfumes.

When decarburization occurs, generally at the hot surface of the steelwire, and in the presence of water vapor resulting from combustion ofgases like natural gas, the wire is unfit for subsequent conversion.Additionally the wire may exhibit property degradation such as lowstrength, low fatigue life, and/or unsuitable draw ability. Applicationof a coating to the surface of the wire, like electroplated copper, actsas a barrier between the wire and atmosphere within the furnace.Although copper oxides, CuO and/or Cu₂O, will form at the surface of thesteel wire, it is possible to apply enough copper to preclude theformation of iron oxides. It is also known in the art that carbon doesnot mix with or diffuse through copper, preventing the possibility ofdecarburization. It is also known that the rate of diffusion of copperinto steel is slow, making it unlikely for copper-steel alloys to format the surface of the wire.

It is known in the heat-treating industry to use electroplated copper asa “mask” during carburizing to prevent carbon from entering the surfaceof certain portions of a part that is intended to be hardened using acarburizing method, e.g. areas that will require subsequent machining.However, copper is not known or used in the art as a “mask” to preventcarbon from leaving the surface of a steel part.

Currently, during direct-fired gas annealing, precautions are taken tohelp ensure that decarburization is avoided or minimized. In general,furnace atmospheres are set to be oxygen-rich in about the first 20percent of the furnace when the wires are still relatively cool. Thisatmosphere is not only conducive to convective heat transfer, thedominant type of heat transfer below a wire temperature of about 700°C., but also it causes a relatively thin layer of tenacious iron oxideto form. Generally, the remaining 80 percent of the atmosphere of thefurnace is setup to run gas-rich with increasing amounts of gas locateddeeper within the furnace.

The amounts of gas present in a furnace are generally determined bymeasuring the carbon monoxide, CO, or oxygen, O₂, level in a specificfurnace zone. This measurement is then utilized to back-calculate theamount of excess gas. For example, if a five-zone furnace is used, thefirst zone would commonly be set slightly oxygen-rich or about 1.5percent oxygen, the second zone to stoichiometric, the third zone withabout 0.9 percent carbon monoxide, the fourth zone with about 1.5percent carbon monoxide and the fifth zone about 2.2 percent carbonmonoxide. The absence of oxygen in the latter portion of the furnacehelps to limit the amount of oxide formed deep in the furnace when thewires are the hottest. The reaction between iron, Fe, and oxygen, O₂,increases rapidly as the wire temperature increases.

Additionally, tri-atomic and more complex gases, like methane, CH₄, helpimprove radiant heat transfer that is dominant and exponential after thewire temperature exceeds about 700° C. Furthermore, presence of gasescontaining carbon, such as carbon monoxide, CO, and methane, CH₄, helpreduce the propensity for decarburization by slightly increasing thecarbon potential in the furnace atmosphere. The final precaution knownin the art and currently taken during strand annealing of wire productsis to carefully monitor the temperature of the steel wire at the exit ofthe furnace. This is completed directly by measuring individual wiretemperatures using an instrument such as a disappearing element opticalpyrometer. This is completed indirectly by measuring the ductility ofthe heat-treated wire by pulling samples in a uniaxial tensile testerand measuring either the elongation during the test or the reduction ofarea at fracture. It is very difficult to control both the wiretemperature and the furnace atmosphere; any shift in the furnaceatmosphere will result in a change in the wire temperature.

Furnace atmospheres can shift due to changes in outside barometricpressure which results in a change in the resistance to furnaceatmosphere gases leaving the furnace exhaust stack. For example, if theoutside barometric pressure decreases, less pressure will be availableto hold the furnace atmosphere in the furnace. Generally, furnace stacksare at the furnace entrance. Therefore, the gas-rich portion of thefurnace shifts toward the furnace entrance, reducing the oxygen-richzone and resulting in a decrease in convective heat transfer and acorresponding decrease in wire temperature.

Another method known in the art to control oxidization anddecarburization is to use a protective atmosphere in the furnace likehydrogen, carbon monoxide, cracked ammonia, or nitrogen, singularly orin combination. In this case a specialized furnace is constructed. Sucha specialized furnace is generally a muffle furnace or a tube furnace.Both of these furnaces, by definition, heat wire indirectly and arerelatively energy inefficient. In addition, cost to produce and maintainsuch a furnace atmosphere in a strand furnace, which is open at bothends, is prohibitively expensive. From an economic standpoint, it isless expensive to use the first method described to help controloxidization and decarburization in a direct-fired gas furnace.

These and other problems exist. Previous attempts to solve these andother problems include the following.

U.S. Pat. No. 4,966,659, issued to Seto et al. on Oct. 30, 1990,discloses a method and apparatus for molten salt electroplating a steelmember in which the surface of the steel member is activated by anodictreatment and the molten salt electroplating is performed on theactivated surface of said steel member.

U.S. Pat. No. 4,745,002, issued to Vexler et al. on May 17, 1988,discloses a method of making a copper clad conductor by the impinging ofcopper particles upon a heated steel wire to cause adhesion of theparticles to the wire, by coalescence, building up the particles to forma coating and then drawing the coated wire to the required diameter. Thecoated wire may be heat treated to cause flow of copper to improve thesurface finish before the drawing process. The copper particles may bedirected at the wire by a spraying technique. Alternatively, the wire ispassed over a fluidized bed of the particles and through a cloud ofparticles thrown up by the bed.

U.S. Pat. No. 4,704,337, issued to Coppens et al. on Nov. 3, 1987,discloses a rubber adherable steel reinforcing element with a compositesurface coating. The steel element for reinforcing a rubber articlecomprises a brass layer and at least one additional outer film of metalor metal alloy selected from the group containing Fe, Ni, Mn, Cr, Mb,Va, Ti, Zi, Nb, Ta, Hf and W.

U.S. Pat. No. 4,686,153, issued to Tominaga et al. on Aug. 11, 1987,discloses an electrode wire for wire electric discharge machining aworkpiece at high speed and high accuracy and a process for preparingthe same. The electrode wire comprises a core wire made of a copper cladsteel wire, 10 to 70% of the sectional area of the copper clad steelwire being occupied by copper, and a copper-zinc alloy layer coveringthe core wire. The copper-zinc alloy layer is prepared by coating thecore wire with zinc by electroplating or hot galvanizing, followed byheating to disperse copper in the zinc layer to convert the same into acopper-zinc alloy layer wherein the concentration of zinc is increasedgradually along the radially outward direction. The preferable thicknessof the copper-zinc alloy layer ranges from 0.1 to 15 microns and theaverage concentration of zinc in the copper-zinc alloy layer ispreferably less than 50% by weight but not less than 10% by weight.

U.S. Pat. No. 4,155,816, issued to Marencak on May 22, 1979 discloses amethod of treating ferrous-based wire comprised of electroplating anegatively charged ferrous based wire in a prescribed aqueouselectrolyte solution containing a positively charged stationary anodeand, in combination, simultaneously, in the same electrolyte solution,and deplating a similarly electroplated ferrous based wire by passingsaid plated wire as a supplemental, additional, positively charged,moving anode through said solution to effect a removal of itselectroplated outer metal coating.

U.S. Pat. No. 3,630,057, issued to Strohmeier on Dec. 28, 1971 disclosesa process and apparatus for manufacturing copper-plated steel wire.Drawing grease is applied to continuously advancing steel wire rod,which is subsequently drawn in succession through a plurality of drawingdies to form wire, which is continuously advanced along a predeterminedpath. Electric current is passed through the advancing wire along apredetermined portion of the path to heat and anneal the wire. Theadvancing wire, which has been annealed, is pickled in an electrolyticbath and is subsequently rinsed and thereafter subjected to a chemicalcopper-plating treatment in a bath consisting mainly of copper sulfatesolution. Drawing grease is applied to the advancing copper-plated wire,which is subsequently drawn through at least one drawing die. Theadvancing wire which has been drawn is finally wound on spools.

The foregoing patent and other information reflect the state of the artof which the inventor is aware and are tendered with a view towarddischarging the inventor's acknowledged duty of candor in disclosinginformation that may be pertinent to the patentability of the technologydescribed herein. It is respectfully stipulated, however, that theforegoing patent and other information do not teach or render obvious,singly or when considered in combination, the inventor's claimedinvention.

BRIEF SUMMARY OF THE INVENTION

In various exemplary embodiments, the technology described hereinprovides systems and methods to prevent iron oxide formation anddecarburization during strand heat treating of a steel product withoutthe required use of acid pickling. Additionally, this technologyprovides placing a coating, such as copper pyrophosphate electrolyticplating, copper sulfate electrolytic plating or hot dip copper plating,to the surface of a steel wire prior to strand heat treating to avoidboth the iron oxide formation and decarburization through the surface ofthe steel wire by preventing interactions between the steel wire and thefurnace atmosphere. Other comparable uses are also contemplated herein,as will be obvious to those of ordinary skill in the art.

In one exemplary embodiment, the technology provides a method to preventiron oxide formation and decarburization during the patenting of steelwire. The method includes coating a steel wire with a metal platingprior to heat treating the steel wire, thereby masking the steel toprevent carbon from leaving a surface of the steel wire. The methodincludes austenitizing the plated steel wire in a gas furnace, whereinthe steel wire is protected against iron oxide formation anddecarburization, which would otherwise occur as a result of exposure tothe atmosphere of the furnace, because of the plating. The methodincludes immediately cooling the austenitized and metal plated steelwire in a controlled cooling process environment. The method includesreducing oxides formed by the oxidation of the metal plating in theatmosphere of the furnace. The method also includes cooling the steelwire to room temperature. The coating of the steel wire with the metalplating prior to heat treating prevents iron oxide formation anddecarburization during the heat treating, without a required use of acidpickling. The coating used for metal plating a steel wire is anelectrolytic copper pyrophosphate plating, and electrolytic coppersulfate coating or hot dip copper plating. The method also includesaustenitizing the plated steel wire in a gas furnace to a temperature of950° C. to 1050° C. and cooling the steel wire to within the range of500° C. to 650° C.

The method also includes reducing oxides formed by the oxidation of themetal plating in the atmosphere of the furnace by passing the steel wirethrough a reducing gas, wherein the reducing gas is hydrogen, carbonmonoxide, or other reducing gas. Alternatively, the method reducesoxides formed by the oxidation of the metal plating in the atmosphere ofthe furnace using reverse plating, after the cooling of the steel wireto room temperature, by a copper pyrophosphate electrolytic removalprocess. Alternatively, the method reduces oxides formed by theoxidation of the metal plating in the atmosphere of the furnace usingreverse plating, after the cooling of the steel wire to roomtemperature, by a copper sulfate electrolytic removal process. Therecovered plating is applied to an unplated steel wire prior to itsaustenization. Alternatively, the method reduces oxides formed by theoxidation of the metal plating in the atmosphere of the furnace by usingacid pickling and rinsing with water the steel wire to remove the acidused in the acid pickling. Alternatively, the method removes oxidesformed by the oxidation of the metal plating in the atmosphere of thefurnace using mechanical descaling of the oxides with mechanicalbrushes.

The method also includes lightly etching, with a mild acid solution, thesteel wire to help improve subsequent electroplating. This etching issubsequent to the reducing of oxides formed. The method also includes,prior to coating a steel wire rod with a metal plating, drawing thesteel wire from a steel wire rod taken from a steel coil, descaling thesteel wire of any mill scale, or preexisting iron oxides used to preventfurther oxidation during shipment, and rinsing the steel wire to removeany extraneous debris from the surface of the wire.

In another exemplary embodiment, the technology provides a system forpreventing iron oxide formation and decarburization during steelpatenting. The system includes a plating device for coating a steel wirewith a metal plating prior to heat treating the steel wire and therebymasking the steel to prevent carbon from leaving a surface of the steelwire. The system includes a tempering device for austenitizing theplated steel wire in a gas furnace, wherein the steel wire is protectedagainst iron oxide formation and decarburization, which would otherwiseoccur as a result of exposure to the atmosphere of the furnace, becauseof the plating. The system includes a controlled cooling device forimmediately cooling the austenitized and metal plated steel wire. Thesystem also includes a device for reducing oxides formed by theoxidation of the metal plating in the atmosphere of the furnace. Thecoating of the steel wire with the metal plating prior to heat treatingprevents iron oxide formation and decarburization during the heattreating, without a required use of electrolytic acid pickling. In oneembodiment, the device for reducing oxides formed by the oxidation ofthe metal plating in the atmosphere of the furnace is a chamber ofhydrogen gas through which the steel wire is passed.

Advantageously, this technology provides a method and system to preventiron oxide formation and decarburization during strand heat treating ofa steel product without the required use of acid pickling. Additionally,this technology provides placing a coating, such as copper pyrophosphateelectrolytic plating, to the surface of a steel wire prior to strandheat treating to avoid both the iron oxide formation and decarburizationthrough the surface of the steel wire by preventing interactions betweenthe steel wire and the furnace atmosphere.

There has thus been outlined, rather broadly, the more importantfeatures of the technology in order that the detailed descriptionthereof that follows may be better understood, and in order that thepresent contribution to the art may be better appreciated. There areadditional features of the technology that will be described hereinafterand which will form the subject matter of the claims appended hereto. Inthis respect, before explaining at least one embodiment of thetechnology in detail, it is to be understood that the invention is notlimited in its application to the details of construction and to thearrangements of the components set forth in the following description orillustrated in the drawings. The technology described herein is capableof other embodiments and of being practiced and carried out in variousways. Also, it is to be understood that the phraseology and terminologyemployed herein are for the purpose of description and should not beregarded as limiting.

As such, those skilled in the art will appreciate that the conception,upon which this disclosure is based, may readily be utilized as a basisfor the designing of other structures, methods and systems for carryingout the several purposes of the present invention. It is important,therefore, that the claims be regarded as including such equivalentconstructions insofar as they do not depart from the spirit and scope ofthe technology described herein.

Further objects and advantages of the technology described herein willbe apparent from the following detailed description of a presentlypreferred embodiment which is illustrated schematically in theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The technology described herein is illustrated with reference to thevarious drawings, in which like reference numbers denote like systemcomponents and/or method steps, respectively, and in which:

FIG. 1 is a flowchart diagram illustrating the process to prepare anintermediate product for heat treating from 5.5 mm steel rod, forexample, according to an embodiment of the present invention; and

FIG. 2 is a flowchart diagram illustrating process steps from thebeginning of wire heat treating through the application of electrolyticcopper, according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Before describing the disclosed embodiments of this technology indetail, it is to be understood that the technology is not limited in itsapplication to the details of the particular arrangement shown heresince the technology described is capable of other embodiments. Also,the terminology used herein is for the purpose of description and not oflimitation.

In various exemplary embodiments, the technology described hereinprovides systems and methods to prevent iron oxide formation anddecarburization during strand heat treating of a steel product withoutthe required use of acid pickling. Additionally, this technologyprovides placing a coating, such as copper pyrophosphate electrolyticplating, to the surface of a steel wire prior to strand heat treating toavoid both the iron oxide formation and decarburization through thesurface of the steel wire by preventing interactions between the steelwire and the furnace atmosphere. Furthermore, the technology preventsiron oxide formation and decarburization without the required use ofacid pickling. Other comparable uses are also contemplated herein, aswill be obvious to those of ordinary skill in the art.

This technology uses a coating, such as, but not limited to,electroplated copper, to prevent iron oxide formation anddecarburization during the strand heat treating of steel product. Thiscoating can help guarantee that decarburization is not possible.Additionally, the coating is easily reduced or removed from the surfaceof the wire after it is oxidized in the austenization furnace. Thisprocess yields less environmental impact and minimal dangers of exposurebetween humans and harsh chemicals.

When a copper coating is used, the copper oxide formed in theaustenization furnace is converted to pure copper though use of areduction process using a gas such as, but not limited to, hydrogen. Thereduction process occurs while the wire is still hot. Additional copperplating can be applied directly to this reduced copper with or withoutslight low concentration acid etching.

The copper oxide can be converted back into a raw material for futurecoating applications by reversing the polarity of the electrolyticsource used initially to plate the coating onto the wire. When copper isused as a coating, it can be electroplated using a copper pyrophosphatesolution that is relatively environmentally friendly and not consideredparticularly harmful to people during industrial exposure. To platecopper onto the wire in a copper pyrophosphate (or any other) solution,the wire is cathodic. To plate copper oxide from the wire, the wire isanodic, and the same solution of copper pyrophosphate can be used forboth operations. Alternately, copper oxide is removed chemically using amild solution of pickling acid at higher temperature than normal(chemical reaction rates double for every ten degree increase intemperature), an operation that is much less harmful to the environment.Alternately, the oxidized copper coating is also removed mechanicallyvia brushes or other abrasive means.

During the manufacture of steel tire cord copper is generallyelectroplated on the surface of the wire in-line with the heat-treatingprocess as part of a process to promote adhesion to rubber. In general,the process steps from the beginning of wire heat treating through theapplication of electrolytic copper are: austenitizing, controlledcooling to 500° C. to 650° C., water quenching to room temperature, acidpickling, water rinsing, electrolytic copper pyrophosphate plating.Using this new technology, the preferred process steps from thebeginning of wire heat treating through the application of electrolyticcopper are: electrolytic copper pyrophosphate plating, austenitizing,controlled cooling to 500° C. to 650° C., copper oxide reduction in agas like hydrogen, cooling to room temperature, electrolytic copperpyrophosphate plating. The new process eliminates any requirement foracid pickling.

In addition to the preferred method listed above this technology alsoincludes other methods to utilize a wire coating, like copper, duringthe heat treatment of product intended for steel tire cord applications.

In one alternative embodiment, the method includes the following stepsin order: electrolytic copper pyrophosphate plating, austenitizing,controlled cooling to 500° C. to 650° C., copper oxide reduction in agas like hydrogen, cooling to room temperature, light etching with amild acid solution to help improve subsequent electroplating, andelectrolytic copper pyrophosphate plating.

In another alternative embodiment, the method includes the followingsteps in order: electrolytic copper pyrophosphate plating,austenitizing, controlled cooling to 500° C. to 650° C., cooling to roomtemperature, reverse plating of copper oxide from the wire's surface(wire anodic), and electrolytic copper pyrophosphate plating. In thiscase, copper oxide plated from the surface of the wire is reused toapply copper to other unplated wire prior to austenization.

In yet another alternative embodiment, the method includes the followingsteps in order: electrolytic copper pyrophosphate plating,austenitizing, controlled cooling to 500° C. to 650° C., cooling to roomtemperature, acid pickling to remove copper oxide, water rinsing, andelectrolytic copper pyrophosphate plating.

In still yet another alternative embodiment, the method includes thefollowing steps in order: electrolytic copper pyrophosphate plating,austenitizing, controlled cooling to 500° C. to 650° C., cooling to roomtemperature, brush descaling or other mechanical methods to removecopper oxide, light acid etching to promote subsequent electroplating,water rinsing, and electrolytic copper pyrophosphate plating.

Prior to heat treating during the manufacture of steel tire cord, steelwire rod, which is generally 5.5 mm in diameter, is reduced to certainin-process sizes ranging from about 0.75 mm to 2.5 mm depending uponfinal product requirements generally using at least one dry drawingprocess. The as-received 5.5 mm rod is covered with iron oxides referredto as mill scale. Mill scale is intentionally left on the surface of therod to help protect the steel from further oxidation (rusting) duringshipment and to a lesser degree to help prevent handling damage likescratches on the surface of the wire rod.

In general, the operations to prepare an intermediate product for heattreating from 5.5 mm rod are as follows: rod payoff from coils, millscale removal, drawing precoat application, forced air drying, drawingthrough tungsten carbide dies, take-up on spools or other in-processcarriers for heat treating and plating as described previously. Somesteel tire cord manufacturers use two dry-drawing steps, optionally withan intermediate heat-treating process.

Although a coating can be applied to wire or wire rod at any time in theprocess prior to heat treating, such as immediately before heattreating, it is preferred in this technology to apply electrolyticcopper, as described, to protect the steel wire during heat-treating, to5.5 mm rod subsequent to mill scale removal and prior to drawing precoatapplication. It is well recognized in the wire drawing industry thatcopper applied to the surface of steel prior to drawing greatly enhancesthe draw ability of the steel (improved amount of material processedbefore changing tungsten carbide die sets due to wear and increaseddrawing speeds). The preferred process steps for application of acoating like copper prior to heat treating is as follows: 5.5 mm steelrod payoff, mill scale removal, rinse in clean water, electrolyticcopper coating, drawing precoat application, forced warm air drying,drawing through tungsten carbide dies, and take-up on spools or otherin-process carriers for heat treating and plating as describedpreviously.

Referring now to FIG. 1, a flowchart 100, illustrating the process toprepare an intermediate product for heat treating from 5.5 mm steel rod,is shown. The flowchart 100 is illustrative of the direction of themovement of the steel wire rod as it is drawn. In this exemplaryembodiment, 5.5 mm steel rod is used for preparation, heat treating, andultimate use in vehicle tires. In step 102, 5.5 mm steel wire rod 118 isdrawn from steel coils. In step 104 the mill scale, or preexisting ironoxides used to prevent further oxidation during shipment, on the steelrod is removed, or descaled. The mill scale is, for example, removedfrom a 5.5 mm steel wire rod that is ultimately intended for themanufacture of steel tire cord. The descaled steel wire rod is rinsed inclean water in step 106. For example, any extraneous debris is cleanedfrom the surface of the wire using a suitable technique like rinsingwith clean hot water. In step 108, the steel wire rod is coated with asufficient coating of an electrolytic copper pyrophosphate plating priorto dry drawing. This coating is designed to ensure that sufficientcopper remains on the surface of the steel wire rod after the first andany subsequent dry drawing operation to ensure protection during heattreating. This coating also masks the steel wire to prevent carbon fromleaving the surface of the steel wire. A drawing precoat application isthen applied to the drawn steel wire rod in step 110 and subsequentlyprecoat dried in step 112 and dry drawn in step 114 with forced warm airdrying. The precoat application 110 is, for example, a liquid precoat,such as borax, or the like, coated onto the plated surface to helpenhance dry drawing ability. The steel wire rod is then drawn through aplurality of tungsten carbide dies using a dry lubricant to help improvelubricity, reducing the 5.5 mm rod's diameter to a prescribed sizeadequate for further processing into tire cord, and subsequently takenup on spools or other in-process carriers in step 116 for heat treatingand plating. This is a preferred process for application of a coatingsuch as copper prior to heat treating.

Referring now to FIG. 2, a flowchart 200, illustrating a preferredmethod to protect the steel wire rod from the atmosphere of the furnaceand methods for copper oxide removal, is shown. The flowchart 200 isillustrative of the direction of the movement of the steel wire rod asit is drawn though each process step. In step 202, the wire drawn from5.5 mm steel rod 218 is to be placed into a heat-treating operation,generally termed patenting, annealing, or tempering. In step 204, anyresidual dry lubricant from the surface of the drawn wire is cleanedusing a commercially acceptable method like immersion in hot cleanwater. In step 206, the steel wire rod is austenitized to a temperaturenear 1000° C. in a suitable direct-fired gas furnace. The furnaceatmosphere is optimized for heat transfer to improve energy efficiency.It is not necessary to set up special furnace atmosphere conditions toprevent scaling or decarburization. In step 208, the austenitized andmetal plated steel wire rod is immediately cooled in a controlledcooling process environment to between 500° C. to 650° C. in order toobtain a microstructure suitable for subsequent drawing for tire cordapplications. In step 210, the steel wire rod is subjected to an oxideremoval process. For example, the steel wire rod, previously plated withan electrolytic copper pyrophosphate plating, is subjected to hydrogengas while the wire temperature is between the soaking temperature androom temperature in order to reduce copper oxides formed duringaustenitizing in the furnace. This requires a standard furnaceatmosphere chamber with built-in cooling. Alternatively, the copperoxide is electroplated from the surface of the wire in a copperpyrophosphate or copper sulfate solution by making the wire anodic. Inthis case, copper plated from the surface of the wire is sold for scrapcopper or reused to re-plate additional 5.5 mm steel wire rod. In step212 the surface of the steel wire rod is mildly etched with a weak acid.Additional conventional processing specific to standard steel tire cordoperations is completed in step 214. The patented and plated wire istaken up in step 216.

Although this technology has been illustrated and described herein withreference to preferred embodiments and specific examples thereof, itwill be readily apparent to those of ordinary skill in the art thatother embodiments and examples can perform similar functions and/orachieve like results. All such equivalent embodiments and examples arewithin the spirit and scope of the invention and are intended to becovered by the following claims.

1. A method to prevent iron oxide formation and decarburization duringthe patenting of steel wire, the method comprising: coating a steel wirewith a metal plating prior to heat treating the steel wire and therebymasking the steel to prevent carbon from leaving a surface of the steelwire; austenitizing the plated steel wire in a gas furnace, wherein thesteel wire is protected against iron oxide formation anddecarburization, which would otherwise occur as a result of exposure tothe atmosphere of the furnace, because of the plating; cooling,immediately, the austenitized and metal plated steel wire in acontrolled cooling process environment; reducing oxides formed by theoxidation of the metal plating in the atmosphere of the furnace and;cooling the steel wire to room temperature; wherein the coating of thesteel wire with the metal plating prior to heat treating prevents ironoxide formation and decarburization during the heat treating, without arequired use of acid pickling.
 2. The method to prevent iron oxideformation and decarburization during steel tempering of claim 1, whereinthe coating used for metal plating a steel wire is an electrolyticcopper pyrophosphate plating.
 3. The method to prevent iron oxideformation and decarburization during steel tempering of claim 1, whereinthe coating used for metal plating a steel wire is an electrolyticcopper sulfate plating.
 4. The method to prevent iron oxide formationand decarburization during steel tempering of claim 1, furthercomprising: austenitizing the plated steel wire in a gas furnace to atemperature of 950° C. to 1050° C.
 5. The method to prevent iron oxideformation and decarburization during steel tempering of claim 1, furthercomprising: cooling the steel wire to within the range of 500° C. to650° C.
 6. The method to prevent iron oxide formation anddecarburization during steel tempering of claim 1, further comprising:reducing oxides formed by the oxidation of the metal plating in theatmosphere of the furnace by passing the steel wire through a reducinggas, wherein the reducing gas is hydrogen.
 7. The method to prevent ironoxide formation and decarburization during steel tempering of claim 1,further comprising: reducing oxides formed by the oxidation of the metalplating in the atmosphere of the furnace by passing the steel wirethrough a reducing gas, wherein the reducing gas is carbon monoxide. 8.The method to prevent iron oxide formation and decarburization duringsteel tempering of claim 1, further comprising: reducing oxides formedby the oxidation of the metal plating in the atmosphere of the furnaceby passing the steel wire through a reducing gas, wherein the reducinggas is a mixture of reducing gases.
 9. The method to prevent iron oxideformation and decarburization during steel tempering of claim 1, furthercompromising: reducing oxides formed by the oxidation of the metalplating in the atmosphere of the furnace by a copper pyrophosphateelectrolytic removal process.
 10. The method to prevent iron oxideformation and decarburization during steel tempering of claim 1, furthercompromising: reducing oxides formed by the oxidation of the metalplating in the atmosphere of the furnace by a copper sulfateelectrolytic removal process.
 11. The method to prevent iron oxideformation and decarburization during steel tempering of claim 1, furthercomprising: reducing oxides formed by the oxidation of the metal platingin the atmosphere of the furnace using acid pickling; and rinsing withwater the steel wire to remove the acid used in the acid pickling. 12.The method to prevent iron oxide formation and decarburization duringsteel tempering of claim 1, further comprising: reducing oxides formedby the oxidation of the metal plating in the atmosphere of the furnaceusing mechanical descaling of the oxides with mechanical brushes. 13.The method to prevent iron oxide formation and decarburization duringsteel tempering of claim 1, further comprising: plating, reversely, andafter the cooling of the steel wire to room temperature, the oxides onthe surface of the wire formed by the oxidation of the metal plating inthe atmosphere of the furnace; and reusing the plating to apply it to anunplated steel wire prior to its austenization.
 14. The method toprevent iron oxide formation and decarburization during steel temperingof claim 1, further comprising: etching, lightly, subsequent to thereducing of oxides formed, with a mild acid solution, the steel wire tohelp improve subsequent electroplating.
 15. The method to prevent ironoxide formation and decarburization during steel tempering of claim 1,further comprising, prior to coating a steel wire with a metal plating:drawing the steel wire from a steel wire rod taken from a steel coil;descaling the steel wire of any mill scale, or preexisting iron oxidesused to prevent further oxidation during shipment; and rinsing the steelwire to remove any extraneous debris from the surface of the wire.
 16. Asystem for preventing iron oxide formation and decarburization duringsteel tempering, the system comprising: a plating device for coating asteel wire with a metal plating prior to heat treating the steel wireand thereby masking the steel to prevent carbon from leaving a surfaceof the steel wire; a patenting device for austenitizing the plated steelwire, wherein the steel wire is protected against iron oxide formationand decarburization, which would otherwise occur as a result of exposureto the atmosphere of the furnace, because of the plating; a controlledcooling device for immediately cooling the austenitized and metal platedsteel wire; and a device for reducing oxides formed by the oxidation ofthe metal plating in the atmosphere of the furnace; and wherein thecoating of the steel wire with the metal plating prior to heat treatingprevents iron oxide formation and decarburization during the heattreating, without a required use of electrolytic acid pickling.
 17. Thesystem for preventing iron oxide formation and decarburization duringsteel tempering of claim 16, wherein the tempering device foraustenitizing the plated steel wire is a direct-fired gas furnace. 18.The system for preventing iron oxide formation and decarburizationduring steel tempering of claim 17, wherein the atmosphere of thefurnace is optimized for heat transfer to improve energy efficiency. 19.The system for preventing iron oxide formation and decarburizationduring steel tempering of claim 16, wherein the controlled coolingdevice, for immediately cooling the austenitized and metal plated steelwire, cools the steel wire to within the range of 500° C. to 650° C. inorder to obtain a microstructure subsequent drawing for tire cordapplications.